1. Field of the Invention
The claimed subject matter relates to superconductivity exhibited in semiconductor materials containing high levels of doubly charged impurities, and particularly to superconductivity in semiconductors doped with doubly charged impurities to such a level that the wavefunctions of the doubly charged impurities overlap and the formation of a Bose condensate occurs.
2. The Related Art
Superconductivity is characterized by the absence of electrical resistance and the exclusion of the interior magnetic field. In many materials that exhibit superconductivity, this phenomenon occurs only at very low temperatures on the order of less than approximately 2 degrees Kelvin. Some few materials, such as certain copper oxides, are characterized as being “high temperature superconductors.” The highest temperature at which superconductivity first appears in a material is defined as the “critical temperature” of that superconductive material. A few materials, such as certain copper oxides (Perovskites), are known to exhibit critical temperatures in excess of 77 degrees Kelvin (which is the boiling point of nitrogen at atmospheric pressure). A mercury based cuprate superconductor, for example, has been found that has a critical temperature above 130 degrees Kelvin. For materials with critical temperatures below about 10 degrees Kelvin, difficult and expensive procedures are required to depress their temperatures to the point where superconductivity is exhibited. This limits the practical applications in which they may be employed. High temperature superconductors have been employed in a number of practical applications, including, for example, electromagnets, mass spectrometers, and magnetic separators. There is a recognized need for high temperature superconductors.
In general, the most useful high-temperature superconductors have critical temperatures well above the boiling point of liquid nitrogen (77 degrees Kelvin). Liquid nitrogen is readily available, so it is feasible to utilize the superconducting characteristics of high-temperature superconductors that exhibit critical temperatures above 77 degrees Kelvin for practical applications such as, for example, in MRI machines.
The frictionless flow of bosons is a characteristic of a Bose condensate. Bose condensates are composed of boson particles, such as bound pairs of electrons. Bose condensates are a phase of matter.
Semiconductor materials are conventionally doped with donor or acceptor impurities using one or more widely known and practiced doping procedures. Dopants are conventionally inserted into the crystal lattices of semiconductor materials using such procedures as ion implantation, diffusion, growth from a melt, and epitaxial techniques such as molecular beam epitaxy or vapor phase epitaxy.
Donor dopants provide electrons, and acceptor dopants provide electron-holes. The dopant ions are trapped within the crystal lattices of the semiconductor materials. The dopants are impurities within the crystal lattices of the semiconductors. Doped semiconductor materials are the basic building blocks upon which most electronic devices depend.
A “degenerate” semiconductor is one that has been doped with sufficient donor or acceptor impurities to, among other things, cause the material to act more like a conductor than a semiconductor. The dopant concentrations in most semiconductor devices are generally well below the degenerate level of doping. The properties of degenerate semiconductor materials are generally intermediate between those of metals and semiconductors. The concentration at which a semiconductor becomes degenerate is unique for each semiconductor material-dopant combination. A degenerate condition exists where the wavefunctions of bound electrons or electron acceptors (holes) overlap. Bound electrons are sometimes described herein as donors, and bound electron acceptors are sometimes described as holes. Both are described herein as impurities. Impurities are bound in the crystal lattice of the host semiconductor material. Such bound impurities are described as impurities because they are different from the atoms that make up the pure host crystal lattice, and not to indicate that they are in any sense undesirable.
There is a need for high temperature superconductors. There is a particular need for high temperature superconductors that, for the most part, can be produced using the existing infrastructure that currently exists for the manufacture of doped semiconductors for use in the electronics industry.
In general, dopants in semiconductor materials may act as singly charged or doubly charged impurities depending on the semiconductor material-dopant combination. A vast amount of research has been reported on such combinations with singly charged impurities wherein the semiconductor materials are lightly doped (well below degenerate concentrations). Some reported research has been carried out on semiconductor materials lightly doped (well below the degenerate level of concentration) with doubly charged impurities. Such research has been primarily aimed at developing new semiconductor devices for use in the electronics industry.
A very limited amount of research (compared to the amount devoted to the electronics industry) has been reported on attempts to use semiconductor material-dopant combinations to achieve superconductivity. Superconductivity has been reported, for example, for silicon, silicon carbide, and diamond doped with boron (a single donor), and germanium doped with gallium (a single donor). Some success has been reported in achieving high-temperature superconductivity at temperatures above about 77 degrees Kelvin with certain copper oxide semiconductor materials doped with electron-holes.
Germanium doped with Be or Zn to a concentration of around 1018 Be or Zn atoms per cubic centimeter of Ge have been described for use as doping pieces. The highly doped doping pieces were described as being added to melts of Ge to produce melts with carefully controlled low dopant concentrations in Ge crystals. See Haller et al., U.S. Pat. No. 6,011,810, which is hereby incorporated herein as though fully set forth hereat. In the event of any conflict or inconsistency between the teachings herein and references that are incorporated by reference, the teachings herein shall prevail.